1. Field of the Invention
The present invention relates to an electron beam based inspection apparatus for inspecting defects in patterns formed on the surface of an object to be inspected, and more particularly, to an inspection apparatus useful, for example, in inspecting defects on a wafer in a semiconductor manufacturing process, which includes irradiating an object to be inspected with an electron beam, detecting secondary electrons which vary in accordance with the properties of the surface thereof to form image data, and inspecting patterns formed on the surface of the object to be inspected based on the image data at a high throughput, and a method of manufacturing devices at a high yield rate using the inspection apparatus. More specifically, the invention relates to a projection type electron beam inspection apparatus which adopts a area beam and a method of manufacturing devices using the inspection apparatus.
2. Field of the Invention
In semiconductor processes, design rules are reaching 100 nm and the method of production form is evolving from mass production, with a few models, such as a DRAM, into small-lot production with a variety of models such as a SOC (Silicon on chip). This has resulted in an increase in the number of processes, and an improvement in yield for each process is essential; which makes it more important to inspect for defects occurring in each process. The present invention relates to an apparatus to be used in the inspection of a wafer after particular steps in the semiconductor fabrication process, and in particular to an inspection method and apparatus using an electron beam and also to a device manufacturing method using the same.
3. Description of the Related Art and Problems to be Solved by the Invention
4. Description of the Prior Art
In conjunction with a high level of integration of semiconductor devices and a micro-fabrication of patterns thereof, an inspection apparatus with higher resolution and throughput is desired. In order to inspect a wafer substrate with 100 nm design rules for any defects, a resolution equal to or finer than 100 nm is required, and the increased number of processes resulting from large-scale integration of devices calls for an increase in the number of inspections, which consequently requires higher throughput. In addition, as multilayer fabrication of devices has advanced, the apparatus is further required to have a function for detecting contact failures in vias for interconnecting wiring between layers (i.e., electrical defects). In the current trend, an inspection apparatus using optical methods has been typically used, but it is expected that an inspection apparatus using an electron beam may soon enter the mainstream, substituting for inspection apparatus using optical methods, given the requirements of higher resolution and detection of contact failures. The electron beam method, however, has a weak point in that it is inferior to the optical method in throughput.
Accordingly, it is desirable to have an apparatus having higher resolution and throughput and being capable of detecting the electrical defects. It has been known that the resolution of the optical method is limited to ½ of the wavelength of the light to be used, and it is about 0.2 .mu.m in a typical case of visible light being put to practical use.
On the other hand, in the method using an electron beam, typically a scanning electron microscopy method (SEM method) has been put to use, wherein the resolution thereof is 0.1 .mu.m and the inspection time is 8 hours per wafer (20 cm wafer). The electron beam method has the distinctive feature that it is able to inspect for any electrical defects (breaking of wires in the wirings, bad continuity, bad continuity of via). However, the inspection speed (sometimes also referred to as inspection rate) thereof is very low, and so the development of an inspection apparatus with higher inspection speed has been eagerly anticipated.
Generally, since an inspection apparatus is expensive and the throughput thereof is rather lower as compared to other processing apparatuses, the inspection apparatus has been used after an important process, for example, after the process of etching, film deposition, CMP (Chemical-mechanical polishing) flattening or the like.
The scanning method (SEM) using an electron beam will now be described. In the inspection apparatus of SEM method, the electron beam is contracted to be finer (the diameter of this beam corresponds to the resolution thereof) and this fined beam is used to scan a sample so as to irradiate it linearly. On the other hand, moving a stage in the direction normal to the scanning direction allows an observation region to be irradiated by the electron beam as a plane area. The scanning width of the electron beam is typically some 100 .mu.m. Secondary electrons emanating from the sample by the irradiation of said contracted and fined electron beam (referred to as a primary electron beam) are detected by a detector, either a scintillator plus photo-multiplier (i.e., photoelectron multiplier tube) or a detector of semiconductor type (i.e., a PIN diode) or the like. The coordinates for the irradiated locations and an amount of the secondary electrons (signal intensity) are combined and formed into an image, which is stored in some recording medium or displayed on a CRT (a cathode ray tube). The above description illustrates the principles of the SEM (scanning electron microscopy), and defects in a semiconductor wafer (typically made of Si) in the course of processes may be detected from the image obtained in this method. The inspection rate (corresponding to the throughput) is varied depending on the amount (the current value), beam diameter, and speed of response of the primary electron beam. A beam diameter of 0.1 .mu.m (which may be considered to be equivalent to the resolution), a current of 100 nA, and a detector speed of 100 MHz are currently the highest values, and in using those values the inspection rate has been about 8 hours for one wafer having a diameter of 20 cm. This inspection rate, which is extremely low compared to the optical method (not greater than 1/20), has been a serious production problem (drawback).
Also, in regard to the prior art of inspection apparatus related to the present invention, an apparatus using a scanning electron microscope (SEM) has been commercially available. This apparatus involves scanning an object to be inspected with a fine electron beam at very narrow intervals of scanning width, detecting secondary electrons emitted from the object to form a SEM image, and comparing such SEM images of different dies at the same locations to extract defects of the object being inspected.
Conventionally, however, there has been no electron beam based defect inspection apparatus which is completed as a general system.
A defect inspection apparatus which applies SEM requires a long time for defect inspection. In addition, increasing the beam current to improve throughput would cause a degradation of the beam due to the space-charge effect and charging on the wafer with insulating material formed on the surface thereof, thereby failing to produce satisfactory SEM images.
Hitherto, no proposal has been made for the overall structure of an inspection apparatus which takes into account the combination of an electron-optical device for irradiating an object to be inspected with an electron beam, with other subsystems associated therewith for positioning the object to be inspected to for irradiating by the electron-optical device in a clean state, and for aligning the object to be inspected. Further, with the trend of increasing diameters of wafers to be subjected to inspection, the subsystems are also required to cope with wafers of such large diameters.
In view of the problems mentioned above, it is an object of the present invention to provide an inspection apparatus which employs an electron beam based electron-optical system, and achieves harmonization of the electron-optical system with other components, which constitute the inspection apparatus, to improve the throughput.
It is another object of the present invention to provide an inspection apparatus which is capable of efficiently and accurately inspecting an object by improving a loader for carrying the object to be inspected between a cassette for storing objects under inspecting and a stage device for aligning the object to be inspected with respect to the electron-optical system, and devices associated with the loader.
It is a further object of the present invention to provide an inspection apparatus which is capable of solving the problem of charging, experienced in the SEM, to accurately inspect an object.
It is a further object of the present invention to provide a method of manufacturing devices at a high yield rate by inspecting an object such as a wafer, using the inspection apparatus as mentioned above.
Also, with increasing integration of semiconductors, there has been a need for a sensitive inspection apparatus to be used in the semiconductor device manufacturing process for defect inspection in the pattern or the likes in semiconductor wafers. In this regard, there have been electron microscopes used as the inspection apparatus for such defect inspections, as disclosed in Japanese Patent Laid-open Publications Nos. Hei 2-142045 and Hei 5-258703.
For example, in the electron microscope as disclosed in Japanese Patent Laid-open Publication No. Hei 2-142045, an electron beam emitted from an electron gun is converged by an objective lens to irradiate a sample to be inspected, and secondary electrons emitted from the sample are detected by a secondary electron detector. In addition, in this electron microscope, a negative voltage is applied to the sample, and further an E.times.B type filter is arranged between the sample and the secondary electron detector, said filter having an electric field and a magnetic field crossed at right angles.
With such a configuration, this electron microscope allows a high resolution to be obtained by decelerating the electrons irradiated onto the sample by way of the negative voltage applied to the sample.
Further, the application of the negative voltage to the sample helps accelerate the secondary electrons emitted from the sample, and the accelerated secondary electrons are further deflected by the E.times.B type filter toward the secondary electron detector, thus to be efficiently detected by the secondary electron detector.
In those conventional apparatuses using the electron microscope as described above, the electron beam from the electron gun is kept accelerated to be highly energized until just before it impinges onto the sample, by a lens system such as an objective lens with a high voltage applied. Then, the negative voltage applied to the sample decelerates electrons impinging upon the sample, thus allowing a high resolution to be achieved.
However, since the high voltage is applied to the objective lens, while the negative voltage is applied to the sample, there has been a risk that an electric discharge may occur between the objective lens and the sample.
Further, in the electron microscope in the prior art, even in the case where no negative voltage is applied to the sample, if there is a great potential difference between the objective lens and the sample, then it is again feared that the electric discharge may occur between the objective lens and the sample.
Still further, if the voltage applied to the objective lens is set lower in order to deal with a possible electric discharge to the sample, the electrons aren't sufficiently energized, resulting in a poor resolution.
An explanation will be further given for a case where the sample to be inspected is a semiconductor wafer having a via, that is a wiring pattern extending in the approximately vertical direction to the upper-layer and lower-layer wiring planes for providing an electrical connection between the upper layer wiring and the lower layer wiring.
When the semiconductor wafer with the via is inspected for defects by using a conventional electron microscope, a high voltage, for example, a voltage of 10 kV is applied to the objective lens as in the above description. Further, in this case, it is assumed that the semiconductor wafer is grounded. Accordingly, an electric field is generated between the semiconductor wafer and the objective lens.
These conditions could make the electric field more intense in the vicinity of the via on the surface of the semiconductor wafer, thus forming a high electric field. Then, when the electron beam is irradiated onto the via, a large number of secondary electrons is emitted from the via, which is further accelerated by the high electric field in the vicinity of the via. Those accelerated secondary electrons have a sufficient energy (>3 eV) to ionize a residual gas generated by the irradiation of the electron beam onto the semiconductor wafer. Accordingly, the secondary electrons ionize the residual gas so as to generate ionized charged particles.
Then, said ionized charged particles, i.e., the positive ions, are accelerated by the high electric field in the vicinity of the via toward the via to impinge against the via, so that more secondary electrons are emitted from the via. Through a series of these positive feedback, eventually an electric discharge occurs between the objective lens and the semiconductor wafer and damages the pattern or the like on the semiconductor wafer, which has been problematic in the prior art.
Thus, an object of the present invention is to provide an electron gun apparatus which can prevent an electric discharge to a sample being inspected and a method for manufacturing a device by using said electron gun apparatus.
Also, as stated above, an inspection for defects in a mask pattern used in manufacturing a semiconductor device or in a pattern formed on a semiconductor wafer has been performed by the steps of detecting secondary electrons emitted from a sample upon irradiation of a primary electron beam against a surface of the sample, obtaining a pattern image of the sample, and comparing said image with a reference image. Typically, such defect inspection apparatus has been equipped with an E.times.B separator for separating the primary electrons and the secondary electrons.
FIG. 52 shows schematically a typical configuration of a projective electron beam inspection apparatus having an E.times.B separator. An electron beam emitted from an electron gun 721 is formed to be rectangular in shape with a forming aperture (not shown) and reduced in size by the electrostatic lenses 722, thus to be a formed beam of 1.25 mm square at the center of an E.times.B separator 723. The formed beam is deflected by the E.times.B separator 723 so as to be normal to a sample W, and reduced to be ⅕ in size with an electrostatic lens 722, which is then irradiated against the sample W. A beam of the secondary electrons emitted from the sample W has a certain intensity corresponding to the pattern data on the sample W, which is expanded by the electrostatic lenses 724, 741, and then enters into a detector 761. The detector 761 generates an image signal corresponding to the intensity of the received secondary electrons, which is compared with a reference image, thereby detecting any defects in the sample.
The E.times.B separator 723 has a configuration in which an electric field and a magnetic field cross at right angles within a plane orthogonal to the normal of the surface of the sample W (the upward direction on paper), so that it advances the electrons straight forward when the relationship of the electric field, the magnetic field, and the energy and speed of the electrons meets certain criteria, while it deflects the electrons in any case other than the said case. In the inspection apparatus of FIG. 44, the conditions are set so that the secondary electrons are advanced straight ahead.
FIG. 53 shows more precisely the movements of the secondary electrons emitted from the rectangular area on the surface of the sample W, which has been exposed to the primary electron beam. The secondary electrons emitted from the sample surface are magnified with the electrostatic lens 724, and imaged onto a central area 723a of the E.times.B separator 723. Since the electric field and the magnetic field of the E.times.B separator 723 have been set such that the secondary electrons are allowed to be advanced straight ahead, the secondary electrons are thus advanced straight ahead to be magnified with the electrostatic lenses 741-1, 741-2 and 741-3, and then imaged on a target 761a within the detector 761. Then, the electron in the image is multiplied by MCP (Multi Channel Plate, not shown) and is formed into an image by a scintillator, CCD (Charge Coupled Device), or the like (not shown). Reference numerals 732 and 733 respectively designate aperture diaphragms arranged in a secondary optical system.
FIG. 54 shows a schematic configuration of a conventional E.times.B separator and the distribution of an electric field generated by said separator. A pair of parallel plate electrodes 723-1 and 723-2 is used to generate an electric field, and a pair of magnetic poles 723-3 and 723-4 is used to generate a magnetic field orthogonal to said electric field. In this configuration, since the magnetic poles 723-3 and 723-4 are made of metals having the ground potential, the electric field is forced to bend toward the ground sides. Accordingly, the distribution of the electric field is as shown in FIG. 54, and the parallel pattern of the electric field may only be obtained in the small central region.
In the case where an E.times.B separator having such a configuration as described above has been applied to a defect inspection apparatus such as a projective electron beam inspection apparatus, there has been a problem of efficiency in inspection in that the irradiated region of the electron beam cannot be enlarged, in order to perform a precise inspection.
Thus, an another object of the present invention is to provide an E.times.B separator which allows a region including both the electric field and the magnetic field having uniform intensities and cross at right angles to each other, to be expanded in a plane parallel to a sample, and which also allows the outer diameter of the whole body to be reduced. Further, another object of the present invention is to reduce the aberration for the detected image obtained, by means of said E.times.B separator applied to a defect inspection apparatus, thus to conduct the precise defect inspection efficiently.
Also, as stated above, there is a conventional apparatus which, in an inspection of a pattern on a semiconductor wafer or a photo mask with an electron beam, reveals a defect in the following way: primarily it scans the surface of a sample such as the semiconductor wafer or the photo mask, or it scans the sample, by sending the electron beam thereto; secondarily it detects secondary charged particles generated from the surface of said sample to generate image data based on the detected result; and lastly it compares the data per cell or die.
However, the above defect inspection apparatus in the prior art has been problematic in that the irradiation of the electron beam causes the surface of the sample to be charged, and carriers from this charging cause a distortion in the image data, which makes it difficult to detect any defects accurately. When alternatively the electron beam current is reduced to make the distortion by the carriers small enough to resolve the problem of said distortion in the image data, the S/N ratio for the secondary electron signal is adversely affected, so that the possibility of invalid error detection is increased, which has been another problem. Further, it has also been a problem in the prior art that multiple scanning and averaging processes for improving the S/N ratio causes a decrease in throughput.
Therefore, another object of the present invention is to provide an apparatus which prevents any distortion from being caused by charging, or which minimizes such distortions if any, and thereby allows a highly accurate defect inspection to be performed, and also to provide a method for manufacturing a device by using said apparatus.
Also, there has been known an apparatus for inspecting a substrate for any defects in an image formed on the substrate in such a manner that the apparatus irradiates a charged particle beam against a surface of the substrate to scan said surface by said charged particle beam, detects secondary electrons emanated from the surface of the substrate, generates image data from the detected result, and then compares the data for each die to one another to detect those defects.
However, this type of imaging apparatus according to the prior art, including the above-described apparatus that has been disclosed in the publication, has been problematic in that the potential distribution on the surface of the substrate or the object to be inspected is not necessarily uniform and the contrast of the image is insufficient, which may cause distortion.
Therefore, a further object of the present invention is to provide an imaging apparatus having an improved performance in defect detection without any loss of throughput.
Another object of the present invention is to provide an imaging apparatus having an improved performance in defect detection by improving the contrast in an image obtained by the detection of secondary electrons from the object to be inspected.
Still another object of the present invention is to provide an imaging apparatus having improved performance in defect detection by making uniform the potential distribution on the surface of an object to be inspected and thereby improving the contrast, thus reducing distortion, in an image obtained by the detection of secondary electrons from said surface of the object to be inspected.
Yet another object of the present invention is to provide a device manufacturing method in which a sample in the course of processes is evaluated by using such an imaging apparatus as described above.
There has also been one such prior art defect inspection apparatus used conventionally in a semiconductor manufacturing process or the like, which inspects a sample such as a wafer or the like for any defects by detecting secondary electrons emanated by irradiating a primary electron beam onto the sample.
Japanese patent Application Public Disclosure No. 11-132975, for example, discloses a defect inspection apparatus which comprises: an electron beam irradiating section for irradiating an electron beam against a sample; a projecting optical section for image-forming a one-dimensional and/or a two-dimensional image of secondary or reflected electrons, said secondary electrons being emanated in response to shape, material, and variation in potential on the surface of the sample; an electron beam detecting section for outputting a detection signal based on a formed image; an image display section for receiving said detection signal and displaying an electron image of the surface of the sample based thereon; and an electron beam deflecting section for changing the angle of incidence of the electron beam irradiated from the electron beam irradiating section onto the sample and the angle of intake of the secondary or reflected electrons into the projecting optical section. According to this inspection apparatus, the primary electron beam is irradiated onto a surface in a specified rectangular region of the sample wafer of the real device.
However, if the electron beam is irradiated on the surface in a relatively large area of the sample wafer of the real device, due to the sample surface being made of an insulating material such as silicon dioxide or silicon nitride, the electron beam irradiation against the sample surface and associated emanation of secondary electrons from the sample surface causes the sample surface to be positively charged, and an electric field produced by this potential has problematically caused a variety of image disorders in the secondary electron beam image.
The present invention has been made in the light of above-mentioned facts, and an object thereof is to provide an defect inspection apparatus and a defect inspection method that enable an inspection of a sample to be performed with higher accuracy by reducing positive charge builed-up in the surface of the sample, thereby overcoming the problem of disorder associated with this charge-up.
Another object of the present invention is to provide a semiconductor manufacturing method that can improve the yield of devices and prevent delivery of any defective products to market by using an inspection apparatus described above to carry out a defect inspection of a sample.
Further, a stage for accurately positioning a sample in a vacuum atmosphere has been used in an apparatus in which a charged particles beam such as an electron beam is irradiated onto the surface of a sample such as a semiconductor wafer so as to expose the surface of the sample to a pattern of a semiconductor circuit or the like, or so as to inspect a pattern formed on the surface of the sample, or in another apparatus in which the charged particles beam is irradiated onto the sample so as to apply an ultra-precise processing thereto.
When said stage is required to be positioned highly accurately, one structure has been conventionally employed, in which the stage is supported in non-contact manner by a hydrostatic bearing. In this case, the vacuum level in a vacuum chamber is maintained by forming a differential exhausting mechanism for exhausting a high pressure gas in an area of the hydrostatic bearing so that the high pressure gas supplied from the hydrostatic bearing may not be directly exhausted into the vacuum chamber.
FIGS. 55A-55B shows one of the examples of such a stage according to the prior art. In the configuration of FIG. 55A, the tip portion of an optical column 71 or a charged particles beam irradiating section 72 of a charged particles beam apparatus for emitting and irradiating a charged particles beam against a sample is attached to a housing 98 which makes up a vacuum chamber C. The interior of the optical column is exhausted to vacuum through a vacuum pipe 710, as in the chamber C through a vacuum pipe 911. Herein, the charged particles beam is irradiated from the tip portion 72 of the optical column 71 against a sample W such as a wafer or the like placed thereunder.
The sample W is detachably held on a sample table 94, and the sample table 94 is mounted on the upper face of a Y directionally movable unit 95 of an XY stage (hereafter referred to as a stage for simplicity). The above Y directionally movable unit 95 is equipped with a plurality of hydrostatic bearings 90 attached on planes (on both of the right and left faces and also on a bottom face in FIG. 55A) facing to guide planes 96a of an X directionally movable unit 96 of the stage 93, and is allowed to move in the Y direction (lateral direction in FIG. 55B) with a micro gap maintained between the guide planes and itself by said hydrostatic bearings 90. Further, a differential exhausting mechanism is provided surrounding the hydrostatic bearing so that a high-pressure gas supplied to the hydrostatic bearing does not leak into the vacuum chamber C. This is shown in FIG. 56. Doubled grooves 918 and 917 are formed surrounding the hydrostatic bearings 90, and are regularly exhausted to vacuum through a vacuum pipe by a vacuum pump (not shown). Owing to such structure, the Y directionally movable unit 95 is allowed to move freely in the Y direction in the vacuum atmosphere as supported in the non-contact manner. Those doubled grooves 918 and 917 are formed in a plane of the movable unit 95 in which the hydrostatic bearing 90 is arranged, so as to circumscribe said hydrostatic bearing. The structure of the hydrostatic bearing may be any of those conventionally known and its detailed explanation can be omitted here.
The X directionally movable unit 96 having said Y directionally movable unit 95 loaded thereon is formed to be concave in shape with the top face opened, as obviously seen from FIG. 55A, and said X directionally movable unit 95 is also provided with completely similar hydrostatic bearings and grooves, and further the unit 96 is supported in a non-contact manner with respect to the stage 97 so as to be movable freely in the X direction.
Combining said Y directionally movable unit 95 with the X directionally movable unit 96 allows the sample W to be moved to a desired position in the horizontal direction relative to the tip portion of the optical column or the charged particles beam irradiating section 72, so that the charged particles beam can be irradiated to a desired location of the sample.
With the stage including a combination of the hydrostatic bearing and the differential exhausting mechanism as described above, the guide plane 96a or 97a facing the hydrostatic bearing 90 makes a reciprocating motion between a high-pressure atmosphere in the electrostatic bearing portion and a vacuum environment within the chamber while the stage moves. During this reciprocating motion, such gas supply cycle is repeated in which while the guide plane is exposed to the high-pressure atmosphere, the gas is adsorbed onto the guide plane, and upon being exposed to the vacuum environment, the adsorbed gas is desorbed into the environment. Because of this gas supply cycle, every time when the stage moves, it has happened that the vacuum level in the chamber C is lowered, which has caused such problems that the exposure, inspection, or processing with the charged particles beam described above could not be carried out stably, and the sample might be contaminated.
Therefore, an another object of the present invention is to provide a charged particles beam apparatus capable of preventing the degradation of the vacuum level and thereby allow a process such as inspection or processing by a charged particles beam to be carried out stably.
Another object of the present invention is to provide a charged particles beam apparatus having a non-contact supporting mechanism by means of a hydrostatic bearing and a vacuum sealing mechanism by means of a differential exhausting so as to produce a pressure difference between the charged particles beam irradiating region and a supporting section of the hydrostatic bearing.
Still another object of the present invention is to provide a charged particles beam apparatus capable of reducing a gas desorbed from the surface of a part facing to the hydrostatic bearing.
Still another object of the present invention is to provide a defect inspection apparatus for inspecting the surface of a sample or an exposure apparatus for delineating a pattern on a surface of a sample, by using such a charged particles beam apparatus as described above.
Yet another object of the present invention is to provide a semiconductor manufacturing method for manufacturing a semiconductor device by using a charged particles beam apparatus such as described above.
Also, in the conventional stage including a combination of the hydrostatic bearing and the differential exhausting mechanism shown in FIGS. 55A-55B, there have been such problems that because of the differential exhausting mechanism having been added, the structure has become more complicated and its reliability as a stage has decreased while its cost has increased over that of a stage having a hydrostatic bearing used in the atmospheric pressure.
Therefore, another object of the present invention is to provide a charged particles beam apparatus having a simple structure capable of being made compact without employing a differential exhausting mechanism for the XY stage.
Another object of the present invention is to provide a charged particles beam apparatus with a differential exhausting mechanism for exhausting a region on a surface of a sample to which a charged particles beam is to be irradiated, as well as for exhausting the inside of a housing containing an XY stage to vacuum.
Still another object of the present invention is to provide a defect inspection apparatus for inspecting the surface of a sample for defects or an exposing apparatus for delineating a pattern on the surface of the sample by using either of the charged particles beam apparatuses described above.
Yet another object of the present invention is to provide a method for manufacturing a semiconductor device by using either of the charged particles beam apparatuses described above.
Also, as stated above, there has been used in the semiconductor manufacturing processes or the like a defect inspection apparatus for inspecting a sample such as a semiconductor wafer for defects by detecting secondary electrons emitted upon an irradiation of a primary electrons against said sample.
In such defect inspection apparatus, there has been employed a technology in which an image recognition technique is put into practical use to accomplish an automated inspection and to achieve higher efficiency in the inspection. In this technology, a computer carries out a matching operation between pattern image data for a region to be inspected in the sample surface obtained by detecting the secondary electrons and reference image data for the sample surface stored in advance, so that it is automatically determined if there are any defects existing in the sample, based on the operation results.
Recently, especially in the semiconductor manufacturing field, patterns are increasingly miniaturized, and consequently requiring detection of finer defects with high precision and efficiency. Under such condition, even the defect inspection apparatus taking advantage of the image recognition technique described above must further improve its recognition accuracy.
However, there has been such a problem associated with the prior art described above, which is that a position mismatch occurs between the image of the secondary electron beam obtained upon irradiating the primary electron beam against the region to be inspected in the sample surface and the reference image prepared in advance, which decreases the accuracy in defect detection. This position mismatch becomes a serious problem especially when the irradiation region of the primary electron beam is offset to the wafer resulting in the inspection pattern partially being out of the detection image of the secondary electron beam, which could not be handled only with the technology for optimizing a matching region within the detection image. This problem could be a fatal drawback especially in the inspecting of patterns of high precision.
Therefore, a still further object of the present invention is to provide a defect inspection apparatus which can prevent a loss of accuracy in the defect detection possibly caused by a position mismatch between the image of an inspection sample and a reference image.
Another object of the present invention is to provide a semiconductor manufacturing method used in semiconductor device manufacturing processes, which attempts to improve the yield of devices and to prevent any faulty products from being delivered to market by using a defect inspection apparatus as described above for performing a defect detection of a sample.